src/probes/lttng-kretprobes.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * probes/lttng-kretprobes.c
   4  *
   5  * LTTng kretprobes integration module.
   6  *
   7  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <wrapper/kprobes.h>
  12 #include <linux/slab.h>
  13 #include <linux/kref.h>
  14 #include <lttng/events.h>
  15 #include <lttng/events-internal.h>
  16 #include <ringbuffer/frontend_types.h>
  17 #include <wrapper/vmalloc.h>
  18 #include <wrapper/irqflags.h>
  19 #include <lttng/tracer.h>
  20 #include <blacklist/kprobes.h>
  21
  22 enum lttng_kretprobe_type {
  23         EVENT_ENTRY     = 0,
  24         EVENT_EXIT      = 1,
  25 };
  26
  27 struct lttng_krp {
  28         struct kretprobe krp;
  29         struct lttng_kernel_event_common *event[2];     /* ENTRY and EXIT */
  30         struct kref kref_register;
  31         struct kref kref_alloc;
  32 };
  33
  34 static
  35 int _lttng_kretprobes_handler(struct kretprobe_instance *krpi,
  36                               struct pt_regs *regs,
  37                               enum lttng_kretprobe_type type)
  38 {
  39         struct lttng_krp *lttng_krp =
  40                 container_of(lttng_get_kretprobe(krpi), struct lttng_krp, krp);
  41         struct lttng_kernel_event_common *event = lttng_krp->event[type];
  42         struct lttng_kernel_probe_ctx lttng_probe_ctx = {
  43                 .event = event,
  44                 .interruptible = !lttng_regs_irqs_disabled(regs),
  45         };
  46         struct {
  47                 unsigned long ip;
  48                 unsigned long parent_ip;
  49         } payload;
  50
  51         switch (event->type) {
  52         case LTTNG_KERNEL_EVENT_TYPE_RECORDER:
  53         {
  54                 struct lttng_kernel_event_recorder *event_recorder =
  55                         container_of(event, struct lttng_kernel_event_recorder, parent);
  56                 struct lttng_kernel_channel_buffer *chan = event_recorder->chan;
  57
  58                 if (unlikely(!LTTNG_READ_ONCE(chan->parent.session->active)))
  59                         return 0;
  60                 if (unlikely(!LTTNG_READ_ONCE(chan->parent.enabled)))
  61                         return 0;
  62                 break;
  63         }
  64         case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:  /* Fall-through. */
  65         default:
  66                 WARN_ON_ONCE(1);
  67         }
  68
  69         if (unlikely(!LTTNG_READ_ONCE(event->enabled)))
  70                 return 0;
  71
  72         switch (event->type) {
  73         case LTTNG_KERNEL_EVENT_TYPE_RECORDER:
  74         {
  75                 struct lttng_kernel_event_recorder *event_recorder =
  76                         container_of(event, struct lttng_kernel_event_recorder, parent);
  77                 struct lttng_kernel_channel_buffer *chan = event_recorder->chan;
  78                 struct lttng_kernel_ring_buffer_ctx ctx;
  79                 int ret;
  80
  81                 payload.ip = (unsigned long) lttng_get_kretprobe(krpi)->kp.addr;
  82                 payload.parent_ip = (unsigned long) krpi->ret_addr;
  83
  84                 lib_ring_buffer_ctx_init(&ctx, event_recorder, sizeof(payload),
  85                                          lttng_alignof(payload), &lttng_probe_ctx);
  86                 ret = chan->ops->event_reserve(&ctx);
  87                 if (ret < 0)
  88                         return 0;
  89                 lib_ring_buffer_align_ctx(&ctx, lttng_alignof(payload));
  90                 chan->ops->event_write(&ctx, &payload, sizeof(payload));
  91                 chan->ops->event_commit(&ctx);
  92                 break;
  93         }
  94         case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:  /* Fall-through. */
  95         default:
  96                 WARN_ON_ONCE(1);
  97         }
  98         return 0;
  99 }
 100
 101 static
 102 int lttng_kretprobes_handler_entry(struct kretprobe_instance *krpi,
 103                                    struct pt_regs *regs)
 104 {
 105         return _lttng_kretprobes_handler(krpi, regs, EVENT_ENTRY);
 106 }
 107
 108 static
 109 int lttng_kretprobes_handler_exit(struct kretprobe_instance *krpi,
 110                                   struct pt_regs *regs)
 111 {
 112         return _lttng_kretprobes_handler(krpi, regs, EVENT_EXIT);
 113 }
 114
 115 static const struct lttng_kernel_event_field *event_fields[] = {
 116         lttng_kernel_static_event_field("ip",
 117                 lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
 118                 false, false, false),
 119         lttng_kernel_static_event_field("parent_ip",
 120                 lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16),
 121                 false, false, false),
 122 };
 123
 124 static const struct lttng_kernel_tracepoint_class tp_class = {
 125         .nr_fields = ARRAY_SIZE(event_fields),
 126         .fields = event_fields,
 127 };
 128
 129 /*
 130  * Create event description
 131  */
 132 static
 133 int lttng_create_kprobe_event(const char *name, struct lttng_kernel_event_recorder *event_recorder,
 134                               enum lttng_kretprobe_type type)
 135 {
 136         struct lttng_kernel_event_desc *desc;
 137         char *alloc_name;
 138         size_t name_len;
 139         const char *suffix = NULL;
 140         int ret;
 141
 142         desc = kzalloc(sizeof(*desc), GFP_KERNEL);
 143         if (!desc)
 144                 return -ENOMEM;
 145         name_len = strlen(name);
 146         switch (type) {
 147         case EVENT_ENTRY:
 148                 suffix = "_entry";
 149                 break;
 150         case EVENT_EXIT:
 151                 suffix = "_exit";
 152                 break;
 153         }
 154         name_len += strlen(suffix);
 155         alloc_name = kmalloc(name_len + 1, GFP_KERNEL);
 156         if (!alloc_name) {
 157                 ret = -ENOMEM;
 158                 goto error_str;
 159         }
 160         strcpy(alloc_name, name);
 161         strcat(alloc_name, suffix);
 162         desc->event_name = alloc_name;
 163         desc->tp_class = &tp_class;
 164         desc->owner = THIS_MODULE;
 165         event_recorder->priv->parent.desc = desc;
 166
 167         return 0;
 168
 169 error_str:
 170         kfree(desc);
 171         return ret;
 172 }
 173
 174 int lttng_kretprobes_register(const char *name,
 175                            const char *symbol_name,
 176                            uint64_t offset,
 177                            uint64_t addr,
 178                            struct lttng_kernel_event_recorder *event_recorder_entry,
 179                            struct lttng_kernel_event_recorder *event_recorder_exit)
 180 {
 181         int ret;
 182         struct lttng_krp *lttng_krp;
 183
 184         /* Kprobes expects a NULL symbol name if unused */
 185         if (symbol_name[0] == '\0')
 186                 symbol_name = NULL;
 187
 188         ret = lttng_create_kprobe_event(name, event_recorder_entry, EVENT_ENTRY);
 189         if (ret)
 190                 goto error;
 191         ret = lttng_create_kprobe_event(name, event_recorder_exit, EVENT_EXIT);
 192         if (ret)
 193                 goto event_exit_error;
 194         lttng_krp = kzalloc(sizeof(*lttng_krp), GFP_KERNEL);
 195         if (!lttng_krp)
 196                 goto krp_error;
 197         lttng_krp->krp.entry_handler = lttng_kretprobes_handler_entry;
 198         lttng_krp->krp.handler = lttng_kretprobes_handler_exit;
 199         if (symbol_name) {
 200                 char *alloc_symbol;
 201
 202                 alloc_symbol = kstrdup(symbol_name, GFP_KERNEL);
 203                 if (!alloc_symbol) {
 204                         ret = -ENOMEM;
 205                         goto name_error;
 206                 }
 207                 lttng_krp->krp.kp.symbol_name =
 208                         alloc_symbol;
 209                 event_recorder_entry->priv->parent.u.kretprobe.symbol_name =
 210                         alloc_symbol;
 211                 event_recorder_exit->priv->parent.u.kretprobe.symbol_name =
 212                         alloc_symbol;
 213         }
 214         lttng_krp->krp.kp.offset = offset;
 215         lttng_krp->krp.kp.addr = (void *) (unsigned long) addr;
 216
 217         /* Allow probe handler to find event structures */
 218         lttng_krp->event[EVENT_ENTRY] = &event_recorder_entry->parent;
 219         lttng_krp->event[EVENT_EXIT] = &event_recorder_exit->parent;
 220         event_recorder_entry->priv->parent.u.kretprobe.lttng_krp = lttng_krp;
 221         event_recorder_exit->priv->parent.u.kretprobe.lttng_krp = lttng_krp;
 222
 223         /*
 224          * Both events must be unregistered before the kretprobe is
 225          * unregistered. Same for memory allocation.
 226          */
 227         kref_init(&lttng_krp->kref_alloc);
 228         kref_get(&lttng_krp->kref_alloc);       /* inc refcount to 2, no overflow. */
 229         kref_init(&lttng_krp->kref_register);
 230         kref_get(&lttng_krp->kref_register);    /* inc refcount to 2, no overflow. */
 231
 232         /*
 233          * Ensure the memory we just allocated don't trigger page faults.
 234          * Well.. kprobes itself puts the page fault handler on the blacklist,
 235          * but we can never be too careful.
 236          */
 237         wrapper_vmalloc_sync_mappings();
 238
 239         ret = register_kretprobe(&lttng_krp->krp);
 240         if (ret)
 241                 goto register_error;
 242         return 0;
 243
 244 register_error:
 245         kfree(lttng_krp->krp.kp.symbol_name);
 246 name_error:
 247         kfree(lttng_krp);
 248 krp_error:
 249         kfree(event_recorder_exit->priv->parent.desc->event_name);
 250         kfree(event_recorder_exit->priv->parent.desc);
 251 event_exit_error:
 252         kfree(event_recorder_entry->priv->parent.desc->event_name);
 253         kfree(event_recorder_entry->priv->parent.desc);
 254 error:
 255         return ret;
 256 }
 257 EXPORT_SYMBOL_GPL(lttng_kretprobes_register);
 258
 259 static
 260 void _lttng_kretprobes_unregister_release(struct kref *kref)
 261 {
 262         struct lttng_krp *lttng_krp =
 263                 container_of(kref, struct lttng_krp, kref_register);
 264         unregister_kretprobe(&lttng_krp->krp);
 265 }
 266
 267 void lttng_kretprobes_unregister(struct lttng_kernel_event_recorder *event_recorder)
 268 {
 269         kref_put(&event_recorder->priv->parent.u.kretprobe.lttng_krp->kref_register,
 270                 _lttng_kretprobes_unregister_release);
 271 }
 272 EXPORT_SYMBOL_GPL(lttng_kretprobes_unregister);
 273
 274 static
 275 void _lttng_kretprobes_release(struct kref *kref)
 276 {
 277         struct lttng_krp *lttng_krp =
 278                 container_of(kref, struct lttng_krp, kref_alloc);
 279         kfree(lttng_krp->krp.kp.symbol_name);
 280 }
 281
 282 void lttng_kretprobes_destroy_private(struct lttng_kernel_event_recorder *event_recorder)
 283 {
 284         kfree(event_recorder->priv->parent.desc->event_name);
 285         kfree(event_recorder->priv->parent.desc);
 286         kref_put(&event_recorder->priv->parent.u.kretprobe.lttng_krp->kref_alloc,
 287                 _lttng_kretprobes_release);
 288 }
 289 EXPORT_SYMBOL_GPL(lttng_kretprobes_destroy_private);
 290
 291 int lttng_kretprobes_event_enable_state(struct lttng_kernel_event_common *event,
 292                 int enable)
 293 {
 294         struct lttng_kernel_event_common *event_exit;
 295         struct lttng_krp *lttng_krp;
 296
 297         if (event->priv->instrumentation != LTTNG_KERNEL_ABI_KRETPROBE) {
 298                 return -EINVAL;
 299         }
 300         if (event->enabled == enable) {
 301                 return -EBUSY;
 302         }
 303         lttng_krp = event->priv->u.kretprobe.lttng_krp;
 304         event_exit = lttng_krp->event[EVENT_EXIT];
 305         WRITE_ONCE(event->enabled, enable);
 306         WRITE_ONCE(event_exit->enabled, enable);
 307         return 0;
 308 }
 309 EXPORT_SYMBOL_GPL(lttng_kretprobes_event_enable_state);
 310
 311 MODULE_LICENSE("GPL and additional rights");
 312 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 313 MODULE_DESCRIPTION("LTTng kretprobes probes");
 314 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 315         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 316         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 317         LTTNG_MODULES_EXTRAVERSION);